1. Field of the Invention
The present invention relates generally to methods for detecting faults in branch conductors in aircraft wire harnesses, and more particularly to methods for locating faults in aircraft branch conductors and determining the distance to the faults.
2. Description of the Related Art
Many electrical systems, such as those found on aircraft, can be tested for faults and failures resulting from defective or improperly mated connectors, or breaks or shorts in the conductor, e.g., the wire or cable. For example, conductors connecting the cockpit controls to the engines or other aircraft components can have a break in them that may, in extreme circumstances, cause the loss or malfunctioning of a particular system of the aircraft. Therefore, aircraft electrical systems are tested in an attempt to avoid these types of faults and failures.
In order to test these systems, each conductor can be individually and separately tested to ensure that it is operating and functioning correctly. Before the testing is performed, however, the conductors are generally disconnected from the associated electrical system. Once a conductor is disconnected, a testing device is used to test for faults and failures.
One testing device used to test conductors for faults and failures is a time domain reflectometry (TDR) device 100, which is shown in block diagram format in FIG. 1. The TDR device 100 includes a signal generator 102 for generating impulse and step signals, a receiver 104 for monitoring, receiving, and sampling (analog or digital) incident, reflected, and response signals, a display 106 for viewing the signals, and a control panel 108 for controlling the signal generator 102, the receiver 104, and the display 106.
FIG. 2 is a front view of the display 106 and control panel 108 of the prior art TDR device of FIG. 1. The control panel 108 includes a number of buttons, control knobs, fields, and indicator lights. For example, the control panel 108 might include a set reference button 200, a cursor distance (or time) field 202, an acquire button 204, a stop acquire button 206, a samples field 208, a fault detect button 210, a short indicator 212, an open indicator 214, a distance to the fault field 216, a conductor field 218, an x-axis units field 220, and a length of the longest conductor or segment field 222. Referring back to FIG. 1, the TDR device 100 also include a supply/return line 110 coupled to the signal generator 102 for propagating the impulse signals and coupled to the receiver 104 for propagating the reflected signals, and a reference line 112 for providing a reference for the impulse and reflected signals. The TDR device 100 transmits and receives impulse and reflected signals across a conductor to determine if the conductor has a fault, e.g., a break or a short, and to determine the distance to the fault. Many other testing devices are also currently available that can be used to test conductors for faults and failures.
To test a conductor, the TDR device 100 is connected to one end of the conductor and transmits an impulse signal towards the other end of the conductor. Since impulse signals respond to changes in impedance, any break or short in the conductor causes an incident signal to be reflected back to the TDR device 100. Having prior knowledge of the length of the conductor, the user can determine if the conductor has a break or short and the distance to the break or short based on the time it takes for the incident signal to return to the TDR device 100. This method for testing is viable for testing a single conductor, however, is not feasible for testing branch conductors that are commonly in aircraft, ship or other vehicle wire harnesses.
Thus, it should be appreciated that there is a need for a break or short test method for aircraft wire harnesses with branch conductors. The present invention fulfils this need as well as others.